Dielectric Ceramics Grain Control for MLCC Reliability
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Solution Overview
Problem
Multilayer ceramic capacitors with fine barium titanate powder exhibit abnormal grain growth during firing, leading to non-uniform crystal grains, lower insulation, and reliability issues, especially at high temperatures, due to the difficulty in achieving both high relative dielectric constant and small grain size.
Innovation Solution
Dielectric ceramics with crystal grains of mean size not exceeding 0.2 μm, primarily composed of barium titanate, are manufactured using liquid phase methods like the sol-gel or hydrothermal synthesis, with zeolitic drying to achieve a high relative dielectric constant and stable temperature characteristics, and multilayer capacitors are fabricated with these ceramics and glass powders to ensure high reliability and insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If barium titanate powder is made finer to reduce dielectric layer thickness, then electrostatic capacity increases and layer thickness decreases, but abnormal grain growth occurs during firing leading to non-uniform crystal grains and lower reliability
Solution Approach 1:
The patent applies preliminary action by pre-coating the surface of fine barium titanate powder particles with glass powder before forming the dielectric layer. This pre-coating prevents abnormal grain growth during subsequent firing processes, ensuring uniform crystal grain sizes even when using very fine powder particles. The glass coating acts as a barrier that controls sintering behavior, allowing the achievement of thin dielectric layers with maintained reliability.
Solution Approach 2:
The patent employs composite materials by creating a core-shell structure where fine barium titanate powder particles are coated with glass powder. This composite structure combines the high dielectric constant of barium titanate with the grain growth抑制 properties of glass. The glass coating layer controls the sintering process and prevents excessive grain growth, enabling the use of ultra-fine particles while maintaining uniform grain size distribution and high reliability in the final ceramic product.
2Stability of the object's composition
If barium titanate powder is made finer to increase relative dielectric constant, then relative dielectric constant improves, but insulation decreases due to abnormal grain growth
Solution Approach 1:
The patent applies preliminary action by pre-coating the surface of fine barium titanate powder particles with glass powder before forming the dielectric layer. This pre-coating prevents abnormal grain growth during subsequent firing processes, ensuring uniform crystal grain sizes even when using very fine powder particles. The glass coating acts as a barrier that controls sintering behavior, allowing the achievement of thin dielectric layers with maintained reliability.
Solution Approach 2:
The patent employs composite materials by creating a core-shell structure where fine barium titanate powder particles are coated with glass powder. This composite structure combines the high dielectric constant of barium titanate with the grain growth抑制 properties of glass. The glass coating layer controls the sintering process and prevents excessive grain growth, enabling the use of ultra-fine particles while maintaining uniform grain size distribution and high reliability in the final ceramic product.
3Quantity of substance
If dielectric layer is made thinner to increase electrostatic capacity, then capacity increases, but abnormal grain growth occurs leading to lower insulation and reliability
Solution Approach 1:
The patent applies preliminary action by pre-coating the surface of fine barium titanate powder particles with glass powder before forming the dielectric layer. This pre-coating prevents abnormal grain growth during subsequent firing processes, ensuring uniform crystal grain sizes even when using very fine powder particles. The glass coating acts as a barrier that controls sintering behavior, allowing the achievement of thin dielectric layers with maintained reliability.
Solution Approach 2:
The patent employs composite materials by creating a core-shell structure where fine barium titanate powder particles are coated with glass powder. This composite structure combines the high dielectric constant of barium titanate with the grain growth抑制 properties of glass. The glass coating layer controls the sintering process and prevents excessive grain growth, enabling the use of ultra-fine particles while maintaining uniform grain size distribution and high reliability in the final ceramic product.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach results in multilayer ceramic capacitors with high relative dielectric constant, stable temperature characteristics, and improved reliability, even with thinner dielectric layers, by controlling grain size and lattice constants, and enhancing insulation and electrostatic capacity.
Implementation Method 1
drying with zeolite at a temperature of 300 to 500°C. to obtain dielectric powder
Implementation Method 2
enhancing electrostatic capacity
Data Source
AI summary
Crystal grains mainly composed of barium titanate have a mean grain size of not more than 0.2 μm. The volume per unit cell V that is represented by a product of lattice constant (a, b, c) figured out from the X-ray diffraction pattern of the crystal grains is not more than 0.0643 nm3. Thereby, a dielectric ceramics having high relative dielectric constant can be obtained. A multilayer ceramic capacitor comprises a capacitor body and an external electrode that is formed at both ends of the capacitor body. The capacitor body comprises dielectric layers composed of the dielectric ceramics, and internal electrode layers. The dielectric layers and the internal electrode layers are alternately laminated.